| Considering that the extracellular matrix of natural bone consists of organic and inorganic compositions, we paid significant attention to organic/inorganic composite applied in bone regeneration. In this study, two series of scaffolds, polycaprolactone/nano-hydroxyapatite (PCL/nHA) and chitosan/nano-hydroxyapatite (CS/nHA), were fabricated and characterized, and they were investigated for the application in bone tissue engineering.PCL/nHA scaffolds were fabricated by a modified melt-molding/leaching technique using NaCl and PEG as co-porogens. Their porous structures were created by the extraction of NaCl particulates and continuous PEG phase. This study mainly investigated the effects of the change of nHA contents and porogens on the basic characteristics of PCL/nHA scaffolds. (1) The porous scaffolds prepared with different nHA contents:The original scaffolds had high porosity at around 70% and showed decreasing compressive modulus (from 24.48 to 2.69 MPa for hydrated scaffolds) with the introduction of nHA. It was noted that the scaffolds could retain relatively stable architecture and mechanical properties for at least six months, although some slight changes happened with the nHA/PCL scaffolds in the mass, the nHA content, the PCL molecular weight and the crystallinity. In the study of enzymatic degradation, porcine pancreas esterase significantly increased the degradation rate of PCL, which also effectively improved the degradation rate of PCL/nHA composite scaffolds. Moreover, during the 7 days culture of bone marrow stromal cells (BMSCs) on scaffolds, the cell adhesion and proliferation of BMSCs were presented well on both the surface and the cross-section of the scaffolds,which indicated that this group of scaffolds had good cytocompatible. (2) The PCL/nHA scaffolds prepared with the different porogens:The PCL/nHA scaffolds exhibited multimodal pore morphologies consisting of macropores and interconnected micropores. The porogens with a fixed proportion of 70% in the blends varied in the NaCl/PEG ratio and the variety of PEG to generate PCL/nHA scaffolds with various pore architectures. The comprehensive modulus was evaluated in the range of 1-18 MPa for scaffolds at hydrated state and showed no significant changes of degradation after the incubation of 24 weeks in PBS solution. Chondrocytes were seeded into the sterilized PCL/nHA scaffolds to estimate the cell-scaffold interactions in vitro, which was investigated by SEM and MTT assay. The PCL/nHA scaffold prepared from NaCl/PEG4000 of 20/50 (PHS-3) presented more macropores with interconnectivity and showed higher strength and improved cytocompatible than the others.CS/nHA composite scaffolds were fabricated by lyophilization from the CS/nHA gel generated by NaHCO3 as an additive. We mostly investigate the effects of the difference ratios of CS/nHA, the addition of NaHCO3 and the washing by basic aqueous solution after molding on the basic characteristics of CS/nHA scaffolds. This method could solve the crack problem arising in the traditional lyophilizing process. The additive NaHCO3 acted as neutralizing agent avoiding possible cytotoxicity, and the bubble generated by neutralization could improve the porosity of scaffolds. Although the CHS-1 scaffold (CS/nHA=30/70) presented high porosity (87.8%) and good cytocompatible, its mechanical property could not satisfy the requirement of bone tissue engineering. Generally, increasing the nHA content could improve the mechanical property of the scaffolds in a certain extent. There were no significant differences in the basic characteristics happened between CHS-2 scaffolds (CS/nHA=20/80, not washed by basic solution) and CHS-3 scaffolds (CS/nHA=20/80, washed by basic solution), and they both had the good cytocompatible, which could meet the need of bone tissue repair.
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